An inductive device typically includes a wire surrounding a common core, with this relatively small diameter wire usually wound on a spool or bobbin. The wound wire, termed "magnet wire", becomes a magnet when charged. Transformers are typical inductive devices which transfer energy from one circuit to another by electromagnetic induction, usually utilizing a secondary winding to provide a transformed voltage output. Generally, a wire bobbin is made from plastic or some other insulating material, and comprises a wire winding center, or hub over which a wire is wound, with side walls for retaining the wire thereon.
Most wire bobbins for inductive devices include termination boxes disposed on one or both of the opposing side walls for attaching lead wires to the beginning and end of the wound wire. The pair of lead wires, which are of substantially greater diameter than the magnet wire, provide the electrical supply to the magnet wire. The termination boxes extend outwardly away from the side walls, with the boxes sized to accept a wire anchor therein. The magnet wire extends through a slot in the box for attachment to the conductive anchor, with the lead wire then inserted into an opening in the anchor which has inwardly sloped fingers which grip the lead wire to prevent withdrawal.
While such structures are acceptable in many applications, the termination boxes are quite bulky and have proven a problem in various transformer applications. For example, in a certain type ballast transformer for fluorescent light applications, a minimum profile transformer housing is required. Therefore, the wire bobbin must fit within a narrow area, yet maintain the proper width and winding depth to achieve the desired transformer output. The existing bobbin design interferes with the adjacent structures, requiring redesign of either the components or housing. Consequently, a need has arisen to provide near flush termination sites on wire bobbins for inclusion in transformers where space is limited.